BIOLOGY 151 1st Edition Lecture 29 Outline of Last Lecture 1. Plants have mitochondria2. Mitochondria3. Different cells use different biochemistry4. Electron donor and acceptor5. Electron donors and acceptors in eukaryotes6. Prokaryotes7. Cyanobacteria8. Some prokaryotic chemotrophs get energy from reduced organic molecules (organotrophs)Outline of Current Lecture 1. "True" multicellular kingdoms eukaryotic2. Eukaryotes3. Signaling between cells?4. Location of receptor in receiving cell?5. Other than lipids and gases, most signals cannot diffuse through lipid bilayer6. General principles of signal transduction7. Does a transduction step amplify the signal?8. Activated enzymes amplify signal9. "Cascades" of kinases can amplify weak signals10. Feedback of later step onto earlier step11. G proteins, protein kinases only 2 examples of transducing molecules12. cAMP and cGMP 2nd messengersCurrent Lecture - 3/29/15"True" multicellular kindgoms eukaryotic:- fungi - mushrooms, molds, yeast- plants- animals- colony = collection of "individuals"- formed by some prokaryotes and protists (single-celled eukaryotes)Eukaryotes:- single-celled protists - 1st fossils about 1.3-1.8 billion years ago- multicellular eukaryotes - first fossils about 0.5-1 billion years ago?Signaling between cells?:- 1) Via cytoplasmic connections- synctial (fused) cells in fungi can pass everything- plants: plasmodesmata - can pass some RNAs, proteins - animals: small pores that pass small molecules, NOT proteins or nucleic acid polymers- 2) Via extracellular signaling molecule- membrane-bound signal (short range)- secreted signal (short or long range)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- signal binds to receptor protein, changing its shape and activity (signal is ligand for receptor)Location of receptor in receiving cell?:- depends on whether signal can go through lipid bilayer - ex. steroid signals can go through membranes- testosterone, estrogen, etc. - gases that signal can also get through membranes (NO, CO, etc.)- steroids - binds receptor protein in cytoplasm and nucleus- signal "transduction" - how ligand receptor binding is "transduced" into effect- receptor steroid complex is a transcription factor that binds to DNA- turns on transcription of genes with matching enhancer DNAOther than lipids and gases, most signals cannot diffuse through lipid bilayer:- ex. proteins, amino acid signals- receptor is usually transmembrane protein- signal binds receptor- activated receptor activates molecule(s) in cytoplasm, may be one or many more steps- signal transduction - there can be many stepsGeneral principles of signal transduction:- does signal affect entire cell, or only part of cell close to the receptor - does the cell know the direction thesignal is coming from?- does a step cause amplification?- is there positive or negative feedback?- example of signaling pathway that effects the entire cell - signals that turn on (or turn off) transcription- example of localized signal that affects part of cell near receptor - activated receptor changes assembly of nearby microfilamentsDoes a transduction step amplify the signal?:- no amplification if activated molecule only activates one target molecule- amplifies if activated molecule is an enzymeActivated enzymes amplify signal:- ex. protein kinases = enzymes that add phosphates to target proteins, activating or inactivating them"Cascades" of kinases can amplify weak signals:- some steps do not amplify signal- example = activated G protein binds and activates single target protein- inactive G protein binds GDP- receptor causes GTP to bind instead- active G protein binds and activates one other proteinFeedback of later step onto earlier step:- positive feedback - can amplify or lengthen time of signal- negative feedback - can decrease or shorten time of signalG proteins, protein kinases only 2 examples of transducing molecules:- other examples: small non-protein molecules = second messengers- important examples:- lipids - from membrane lipids- Ca2+ - from outside cell or storage in ER- cyclic AMP (cAMP) or cGMPcAMP and cGMP 2nd messengers:- adenylyl cyclases catalyze- cAMP activates protein kinase A- guanlylyl cyclases make cGMP, activates protein kinase G, others- ex. epinephrine (adrenaline) makes liver cells increase glycogen breakdown for
View Full Document
Unlocking...